Concrete formwork system for forming cast in place horizontal slabs

ABSTRACT

A system for forming Cast In Place horizontal concrete slabs, having multiple embodiments together comprising: plywood support modular elements, mounted on joists and/or joist sections, having flanges protruding beyond the joist edges and supporting top plywood sheathing; perpendicular joist support modular elements engaging with plywood support modular elements and providing vertical support to one end of a perpendicular joist and/or joist section; a first set of rows and a second perpendicular set of rows of joists and/or joist sections forming a grid structure for supporting top plywood sheathing further comprising use of the said modular elements to reduce plywood deflection; shoring means; means for rendering a level top horizontal surface of the formwork; means for setting the camber at each intersection perpendicular joists; and means for disassembly of the second set of rows and joists and/or joist sections after the formed slab has partially cured.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of U.S. Application No. 61/011,835 filed Jan. 22, 2008, the contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention comprises a system for forming Cast-In-Place (CIP) horizontal concrete slabs, such as floors of buildings, or bridge decks. These slabs are typically formed by first constructing removable formwork, placing a reinforcing structure, such as steel rebar, on the formwork, and then pouring concrete into the formwork. Although the present invention can be accommodated to use in non-rectangular horizontal slabs, discussion will be limited to forming rectangular horizontal slab sections.

A variety of types of formwork and formwork systems are used by the construction industry. The selection of a suitable formwork system for a given project is generally driven two assessments. First, is the system adequate regarding engineering requirements? Second, what system among multiple available and adequate systems will yield the lowest possible construction cost? Important parameters regarding cost include: material costs, time required to set up the formwork, and time required to tear down the formwork.

Regarding cost, for some projects, such as high rise buildings, the use of sophisticated and expensive formwork systems can be cost justified by the ability to quickly move the formwork from one level to a higher level. For simpler structures, simpler formwork systems may be cost justified, even if their use involves a higher proportion of direct labor for setting up and tearing down.

Regarding design parameters, required or desirable attributes of a formwork system for CIP horizontal concrete slabs comprise: a modular design, such that components can be used to achieve some, but not all, of the benefits of the full system; minimal or no need for nails or other fasteners; practicality of using for formwork elements lighter and less expensive 2× lumber rather than heavier and more expensive 4× lumber; assurance that when plywood sheets abut, their lines of abutment are parallel to and centered on supporting joists; assurance that any deflection resulting during the pouring of concrete will not pull a plywood sheet over the edge of a supporting joist; means to minimize plywood deflection to within acceptable parameters; means to set the level of the formwork upper surface to provide for any required camber, as determined by architectural and engineering specifications, such that when the formwork is removed, and normal deflection occurs in the horizontal slab, the resulting surface of the slab will be flat; means to ensure optimal stability of a shored formwork structure, and means to allow for early removal of cross member joist sections, while leaving in place primary supporting joists, when the concrete has set and cured to a point that the cross member joist sections are no longer needed to prevent deflection between primary supporting joists.

BRIEF DESCRIPTION OF THE INVENTION

The present invention comprises a system for forming Cast-In-Place (CIP) horizontal concrete slabs, such as floors of buildings, or bridge decks. The present invention further comprises one or a plurality of plywood support modular elements, these elements further comprising a top plate and two adjoining side supports, a central joist enclosing cavity for mounting on joists and/or joist sections, and two opposite and protruding flanges perpendicular to the joist. Embodiments of the plywood support modular elements support top plywood sheathing, align sheathing edges with the top center lines of joists and/or joist sections, reduce top plywood sheathing deflection when the formwork is supporting concrete reinforcing elements and/or poured concrete, and ensure that under the weight and/or impact of concrete reinforcing elements and poured concrete, sheathing cannot fall over the edge of a joist and/or joist section, causing a “blown form”. Some embodiments of the present invention further comprise one or a plurality of perpendicular joist support modular elements, which engage with a protruding flange of a plywood support modular element, and vertically support one end of a joist or joist section perpendicular to the joist or joist section supporting the engaged plywood support modular element. Some embodiments of the present invention further comprises grid structures having square or rectangular enclosures formed by the intersections of a first set of parallel rows of joists and/or joists sections with a perpendicular second set of rows of joists and/or joist sections. The rectangular enclosures may further comprise one or a plurality of mounted plywood support modular elements having protruding flanges on an interior side of the rectangular enclosure, providing deflection support for top plywood sheathing when the rectangular enclosure is supporting concrete reinforcing elements and/or poured concrete. Some embodiments of the present invention further comprise means for adjusting the camber for one or more points of intersection of perpendicular joists and/or joist sections, such that when the formwork is removed, the settled cast concrete slab will have a level top surface. Some embodiments of the present invention further comprise means for disassembly and reuse of some formwork elements comprising and engaged with the second set of rows and joists and/or joist sections after the formed slab has partially cured. The present invention comprises further means, including embodiments of vertically sized shim pads, to render the upper face of the formwork as either both level and horizontal, or with camber as needed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top perspective view of a first embodiment of a plywood support modular element.

FIG. 1 a is an exploded top side perspective view of a first embodiment of a plywood support modular element.

FIG. 1 b is a top side perspective view of a first embodiment of a plywood support modular element.

FIG. 1 c is a front view of a first embodiment of a plywood support modular element.

FIG. 2 is a top side perspective view of a first embodiment of a plywood support modular element mounted on a joist section with a protruding nail.

FIG. 2 a is a top side perspective view of a first embodiment of a plywood support modular element mounted on a joist section with a protruding nail and covered by a first top plywood sheathing section.

FIG. 2 b is a top side perspective view of a first embodiment of a plywood support modular element mounted on a joist section with a protruding nail and covered by a first top plywood sheathing section and a second top plywood sheathing section.

FIG. 2 c is a top side perspective view of a first embodiment of a plywood support modular element mounted on a joist section and covered by a first nailed top plywood sheathing section and a second nailed top plywood sheathing section.

FIG. 3 is a top schematic view of an embodiment of the present invention comprising a series of a first embodiment of a plywood support modular elements mounted on primary support joists spanning and supported by two girders.

FIG. 3 a is a top schematic view of an embodiment of the present invention comprising a series of top plywood sheathing sheets mounted on the structure of FIG. 3.

FIG. 3 b is a top schematic view of the plywood sheathing sheets of FIG. 3 a superimposed on the structure of FIG. 3.

FIG. 3 c is a top schematic view of an embodiment of the present invention comprising the plywood sheathing sheets of FIG. 3 a superimposed on a structure of double whalers, stringers, and a first embodiment of a plywood support modular element.

FIG. 4 is an exploded top side perspective view of a first embodiment of a perpendicular joist support modular element and a first embodiment of a side support structure.

FIG. 4 a is a top side perspective view of a first embodiment of a perpendicular joist support modular element engaged with a first embodiment of a side support structure.

FIG. 4 a-1 is an exploded top side perspective view of a second embodiment of a perpendicular joist support modular element, a second embodiment of a plywood support modular element, and a second embodiment of a side support structure.

FIG. 4 a-2 is a top side perspective view of a second embodiment of a perpendicular joist support modular element engaged with a second embodiment of a plywood support modular element.

FIG. 4 b is a top side perspective view of a third embodiment of a perpendicular joist support modular element engaged with a first embodiment of a side support structure.

FIG. 4 c is a top side perspective view of a first embodiment of a perpendicular joist support modular element supporting an end of a first joist section, engaged with a first embodiment of a plywood support modular element mounted on a perpendicular second joist section.

FIG. 4 d is a top side perspective view of the structure of FIG. 4 c, with shim pads supported by the first and second joist sections.

FIG. 4 d-1 is a top side perspective view of a second embodiment of a perpendicular joist support modular element supporting an end of a first joist section having a shim pad, engaged with a second embodiment of a plywood support modular element mounted on a perpendicular second joist section having a shim pad.

FIG. 4 e is an exploded top side perspective view of embodiments of formwork elements of the present invention to be engaged at an embodiment of an intersection of a grid structure of the present invention.

FIG. 4 f is a top side perspective view of embodiments of formwork elements of the present invention engaged at an embodiment of an intersection of a grid structure of the present invention.

FIG. 4 g is a top side perspective view of embodiments of formwork elements of the present invention engaged to render an embodiment of a grid rectangle of the present invention.

FIG. 4 g-1 is a top side perspective view of embodiments of formwork elements of the present invention engaged to render an embodiment of a grid rectangle of the present invention, having an exploded first embodiment of a plywood support modular element positioned above a supporting shim pad.

FIG. 5 is a top schematic view of embodiments of formwork elements of the present invention engaged to render an embodiment of a grid structure of the present invention, and illustrating the situation of expanded views of formwork elements with respect to the grid structure.

FIG. 5-1 is an expanded view of embodiments of formwork elements as situated in FIG. 5 with respect to an embodiment of a grid structure of the present invention.

FIG. 5-2 is an expanded view of an embodiment of a shim pad as situated in FIG. 5 with respect to an embodiment of a grid structure of the present invention.

FIG. 5-3 is an expanded view of an embodiment of a shim pad as situated in FIG. 5 with respect to an embodiment of a grid structure of the present invention.

FIG. 5 a is a top schematic view of embodiments of sheets of top plywood sheathing superimposed on embodiments of other formwork elements of the present invention engaged to render a first embodiment of a grid structure of the present invention.

FIG. 5 b is similar to FIG. 5 a, but illustrates rendering of a second embodiment of a grid structure of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates one embodiment of the plywood support modular element, 101, of the present invention, comprising a top plate, 111, and two side support structures, 151, attached to the top plate, 111, by means such as welding. The two side support structures, 151, each have flange sections, 155, that extend to a first edge, 113, of the top plate, 111. The top plate, 111, further comprises a nailing hole, 112, which provides means for fastening the plywood support modular element, 101, to the top of a joist. The side support structures, 151, further comprise an outer peripheral nailing hole, 152, which provides both a means for attaching and securing a second perpendicular joist support modular element, (not illustrated in FIG. 1,) which depends for vertical support on the joist on which a plywood support modular element, 101, rests, and a cost effective means for suspending the plywood support modular element, 101, as it is electroplated.

FIG. 1 a illustrates an exploded view of a plywood support modular element, 101, of the present invention. As illustrated in FIG. 1 a, the side support structures, 151, have upper notches, 153, such that, referring now to FIG. 1 b, when the side support structures, 151, are attached to the top plate, 111, rectangular slots, 154, are formed, and provide a cooperative means for engaging and securing a second perpendicular joist support modular element (not illustrated in the FIG. 1 Series), which depends for vertical support on the joist on which a plywood support modular element, 101, rests.

FIG. 1 c, a front view facing the first edge, 113, of the plywood support modular element, 101, illustrates a central plywood support joist enclosing cavity, 102, formed by the top plate, 111, and the flange sections, 155, of the side support structures, 151. When the plywood support modular element, 101, is mounted on, and depending for vertical support on, a joist, the joist is enclosed on three sides by the plywood support joist enclosing cavity, 102.

FIG. 2 illustrates a plywood support modular element, 101, mounted on top of, and depending for vertical support on, a joist section, 201, having a joist section center line, 202. As described earlier with reference to FIG. 1 c, the joist section, 201, is enclosed on three sides by the plywood support joist enclosing cavity, 102. A nailing hole, 112, goes through the top plate, 111, and adjoins the joist section, 201. A finishing nail, 103, is driven most of its length into the joist section, 201, but protrudes about three fourths of an inch above the top plate, 111. The top plate, 111, the finishing nail, 103, and the flange sections, 155, of the side support structures, 151, combine to prevent the plywood support modular element, 101, from moving horizontally in any direction. FIG. 2 further illustrates that the side structures, 151, together with the top plate, 111, form flange structures, 158, perpendicular to the joist section, 201, extending outward in opposite directions from the upper side, 406, and supported horizontally by the vertical sides of the joist section, 201. FIG. 2 further illustrates that each of the flange structures, 158, comprises a central slot, 154, having a perimeter delineated by the bottom surface of the top plate, 111, and the peripheral edges of the upper notches, 153, in the side support structures, 151. FIG. 2 further illustrates a shim pad, 171, of the present invention, dimensioned to be placed on the upper side of a joist, and to support plywood sheets at the same level as the top of the top plate, 111. In general, shim pads of the present invention should be of substantially incompressible material, and can be secured to the upper sides of joists by means such as adhesive sides of the shim pad covered by a removable release layer, or nailing with short, thin, wide headed nails or tacks.

FIG. 2 a is similar to FIG. 2, but further comprises a first top plywood sheet section, 221, which abuts against the central protruding portion of the finishing nail, 103. Continuing to refer to FIG. 2 a, the first plywood sheet section lower edge, 222, is parallel to, and almost contiguous with, the joist section center line, 202. With respect to the prior art, one advantage offered by the plywood support modular element of the present invention, functioning on a stand-alone basis, is centering the edges of plywood formwork sheathing on the top center lines of joists.

FIG. 2 b is similar to FIG. 2 a, but further comprises a second plywood sheet section, 223, which also abuts against the protruding portion of the finishing nail, 103. Continuing to refer to FIG. 2 b, the second plywood sheet section lower edge, 224, is also parallel to, and almost contiguous with, the joist section center line, 202. There is a gap, 225, between the first plywood sheet section, 221, and the second plywood sheet section, 223, having a width sized by the thickness of the finishing nail, 103. Because concrete does not easily fill small cracks, this gap, 225, may not be a problem for many projects—any concrete that fills it can be ground or scraped off, or left, after the formwork is removed. It should be noted that a small gap between sheets of plywood is sometimes desirable, to allow for expansion caused by temperature and moisture.

FIG. 2 c is similar to FIG. 2 b, but illustrates that the gap, 225, of FIG. 2 b, can be substantially eliminated if necessary. Referring again to FIG. 2 c, once the first plywood sheet section, 221, has been placed and aligned on the joist section, 201, referring now to FIG. 2 a, by means of the protruding finishing nail, 103, referring now to FIG. 2 c, additional plywood securing nails, 104, may be driven through the first plywood sheet section, 221, and into the joist section, 201, thus securing the first plywood sheet section, 221, to the joist section, 201, such that, referring now to FIG. 2 a, the first plywood sheet section lower edge, 222, remains parallel to, and almost intersects, the joist section center line, 202. Referring now to FIG. 2 a, the finishing nail, 103, may then be removed. Referring now to FIG. 2 c, the second plywood sheet section, 223, may now be placed to butt up against the first plywood sheet section, 221, and additional plywood securing nails, 105, may be driven through the second plywood sheet section, 223, and into the joist section, 201, thus securing the second plywood sheet section, 223, to the joist section, 201, such that there is very little or no gap between the first plywood sheet section, 221, and the second plywood sheet section, 223. Alternatively, referring now to FIG. 2 b, any gap between the first plywood sheet section, 221, and the second plywood sheet section, 223, can be reduced or eliminated by following the procedure just outlined with one modification: driving the finishing nail, 103, in fully, rather than removing it.

FIG. 3 illustrates a top view of one embodiment of the present invention comprising a series of primary support joists, 301, perpendicular to, spanning, and supported by two girders, 302, such that the top sides of the primary support joists, 301, form a plane. It should be noted that many structures, including but not limited to: steel I-beams, concrete beams, and supporting walls, can perform a supporting function equivalent to the girders, 202, illustrated in FIG. 3. While the means by which the primary support joists, 301, are supported by the girders, 302, is not illustrated, it should be understood that this could be by hangers, ledgers, or other means. Although there may be many embodiments, having many combinations of dimensions, for purposes of clarity and simplicity, the FIG. 3 Series and FIG. 5 Series illustrations are rendered approximately to scale, and share some common dimensional characteristics that are typical of construction standards in the United States. With reference to FIG. 3, the length of the primary support joists, 301, is twelve feet, and they are spaced a distance of sixteen inches apart. Three of the primary support joists, 301, are also termed short plywood edge primary support joists, 303, and have plywood support modular elements, 101, mounted on them. The plywood support modular elements, 101, are spaced two feet apart, with the exception of the two plywood support modular elements, 101, mounted on each short plywood edge primary support joist, 303, that are nearest the girders, 302. The short plywood edge primary support joists, 303, are spaced eight feet apart, and have center lines, 304, such that, referring now to FIG. 1, the nailing hole, 112, of each plywood support modular element, 101, referring now to FIG. 3, aligns with the center line, 304, when the plywood support modular element, 301, is mounted on the short plywood edge primary support joist, 303.

FIG. 3 a illustrates four foot by eight foot formwork plywood sheets, 351, that have been placed over the series of primary support joists, 301, illustrated in FIG. 3. As will be illustrated further, the short edges, 352, of the formwork plywood sheets, 351, are aligned directly over the center lines, 304, of FIG. 3.

FIG. 3 b further illustrates the relationship between the structure of primary spanning joists, 301, and plywood support modular elements, 101, of FIG. 3, illustrated with dashed lines, and the formwork plywood sheets, 351, of FIG. 3 a, illustrated with solid lines. Continuing to referring to FIG. 3 b, because, as noted earlier with reference to FIG. 3, the top sides of the series of primary spanning joists, 301, form a plane, referring now to FIG. 3 b, all of the primary spanning joists, 301, are engaged in providing vertical support for the formwork plywood sheets, 351. When concrete is poured into the form, the spacing between adjacent primary spanning joists, 301, determines the amount of deflection for the formwork plywood sheets, 351, along their short edges, 352. For a spacing of sixteen inches between adjacent primary spanning joists, 301, plywood deflection will be minimal along the abutting long edges, 353, for slab thickness of up to a foot. When joist spacing is such that plywood deflection is minimal, there is no need to independently support the abutting long edges, 353, of the formwork plywood sheets, 351.

However, as the spacing between primary spanning joists, 301, increases, a potential need arises to support the abutting longer edges, 353, of the formwork plywood sheets, 351, because variation between the strength of individual formwork plywood sheets, 351, and/or variation in the impact forces and the weight of concrete before screeding can result in different degrees of deflection for abutting formwork plywood sheets, 351, forming ridges in the surface of the concrete. In addition, even when ridges can be prevented at the abutting long edges, 353, of formwork plywood sheets, 351, waves in the formed concrete resulting from plywood deflection may be unacceptable.

In addition to the above considerations regarding plywood deflection, as the spacing between adjacent primary spanning joists, 301, is increased, there is an increased danger that in the absence of plywood support modular elements, 101, if the abutting short edges, 352, of two formwork plywood sheets, 351, referring now to FIG. 3, are not aligned directly over the center line, 304, of a short plywood edge primary spanning joist, 303, referring now to FIG. 3 b, the edge of a formwork plywood sheet, 351, may be pulled over the edge of the upper side of a short plywood edge primary spanning joist, 303. The result is dangerous and costly blown formwork. As a minimum consequence, the pour must be stopped until the formwork can be repaired.

The stand alone use of plywood support modular elements, 101, can be of great benefit in ensuring against blown formwork. With assurance against blown formwork, it may be practical to increase the spacing of primary spanning joists, 301, thus reducing costs, up to the limits associated with plywood deflection, discussed above.

FIG. 3 c is similar in some respects to the FIG. 3 Series illustrations discussed above; however, double whalers, 321, spaced four feet apart and having top sides that form a plane, provide the primary spanning support that was provided by the series of primary spanning joists, 301, of FIG. 3 and FIG. 3 b. Continuing to refer to FIG. 3 c, while the means by which the double whalers, 321, are supported by the girders, 302, is not illustrated, it should be understood that this could be by hangers, ledgers, or other means. A series of stringers, 322, spaced sixteen inches apart, are perpendicular to, resting on, and supported by, the double whalers, 321, and also have top sides that form a plane.

Two of the stringers, 322, are also termed long plywood edge stringers, 323, and have plywood support modular elements, 101, mounted on them. The plywood support modular elements, 101, are spaced two feet apart. The long plywood edge stringers, 323, are spaced four feet apart, and have center lines, 324, such that, referring now to FIG. 1, the nailing hole, 112, of the plywood support modular element, 101, referring now to FIG. 3 c, aligns with the center line, 324, when the plywood support modular elements, 301, are mounted on top of the long plywood edge stringers, 301.

Continuing to refer to FIG. 3 c, the spacing of the double whalers, 321, is driven by two considerations: first, the strength and other properties required for function as a load bearing member, and second, the strength and other properties required of the stringers that span the double whalers. When the spacing between the double whalers, 321, is shorter, lighter stringer material, such as 2×4 joists, may be sufficient. As the spacing between both the double whalers, 321, and the stringers, 322, increases, heavier lumber may be required.

FIG. 3 a also serves to illustrate four foot by eight foot formwork plywood sheets, 351, that have been placed on the structure of double whalers, 321, and stringers, 322, illustrated in FIG. 3 c. Referring now to FIG. 3 a, the long edges, 353, of the formwork plywood sheets, 351, referring now to FIG. 3 c, are aligned directly over the center lines, 324, of the long plywood edge stringers, 323.

FIG. 3 c further illustrates the relationship between the structure of double whalers, 321, and stringers, 322, and the formwork plywood sheets, 351, of FIG. 3 a, illustrated with dashed lines in FIG. 3 c. Continuing to refer to FIG. 3 c, because as noted earlier, the upper sides of the series of stringers, 322, form a plane, all of the stringers, 322, are engaged in providing vertical support for the formwork plywood sheets, 351. When concrete is poured into the form, the spacing between adjacent stringers, 322, determines the amount of deflection for the formwork plywood sheets, 351.

As the spacing between stringers, 322, increases, referring now to FIG. 3 a, a potential need arises to support the abutting shorter edges, 352, of the formwork plywood sheets, 351, because variation between the strength of individual formwork plywood sheets, 351, and/or variation in the impact forces and the weight of concrete before screeding can result in different degrees of deflection for abutting formwork plywood sheets, 351, resulting in ridges in the surface of the concrete. In addition, even when ridges can be prevented at the abutting short edges, 352, of formwork plywood sheets, 351, waves in the formed concrete resulting from plywood deflection may be unacceptable.

Referring to FIG. 3 c, a practical stringer spacing limit of two feet emerges with respect to conventional dimensions for formwork construction in the United States using plywood sheets, because there would be a great danger of blown forms if there were no intermediate support from a stringer, 322, between two adjacent long plywood edge stringers, 323. Without intermediate stringer support, should a long edge of a plywood sheet fall over the edge of a stringer, the weight of supported concrete would almost certainly tear the entire sheet loose from the formwork. In addition, for construction in the United States, plywood deflection is greater for the formwork configuration illustrated in FIG. 3 c, because the plywood grain surface runs parallel to the stringers. For this reason, it is particularly desirable to use plywood support modular elements, 101, of the present invention for any formwork configuration where stringers or joists are parallel to the grain of the plywood. Referring to FIG. 3 c, the use of plywood support modular elements, 101, of the present invention decreases the danger that if the abutting long edges of two formwork plywood sheets are not aligned directly over the center line, 324, of a long plywood edge stringer, 323, the edge of a formwork plywood sheet, 351, may be pulled over the edge of the upper side of a long plywood edge primary stringer, 323. The result is dangerous and costly blown formwork. As a minimum consequence, the pour must be stopped until the formwork can be repaired.

For formwork designs having supporting joists or stringers that run parallel to the plywood grain, the stand alone use of plywood support modular elements, 101, of the present invention can be of great benefit in ensuring against blown formwork. With assurance against blown formwork, it may be practical to increase the spacing of stringers, 322, to up to two feet for construction in the United States, thus reducing costs.

The joists or stringers in the FIG. 3 Series illustrations that provide direct support for formwork plywood sheets were all parallel. As illustrated in FIG. 5, it is also possible to have perpendicular joist sections, 404, attached to primary support joists, 301, such that the top sides of the perpendicular joist sections, 404, and the primary support joists, 301, are approximately in the same plane. Before considering in more detail the benefits offered by such a system of formwork joist elements, a second, perpendicular joist support modular element of the present invention will be introduced.

FIG. 4 illustrates one embodiment of a perpendicular joist support modular element, 501, of the present invention, in proximity to a side support structure, 151. Referring to FIG. 1, the illustrated embodiment of the plywood support modular element, 101, of the present invention comprises two of these side support structures, 151. Referring to FIG. 4, the perpendicular joist support modular element, 501, of the present invention comprises a sized section of steel rod, 502, one half inch wide, and one eighth inch thick, that is formed by bending into a rectangular enclosure, 503, dimensioned to a standard size of joist material, such as 2×6 lumber, and an upper protruding flange, 504. At the enclosing intersection, 512, one end of the steel rod, 502, and the upper horizontal section, 510, are joined by means such as welding, such that the rectangular enclosure, 503, can support one end of a load bearing perpendicular joist section.

FIG. 1 b illustrates rectangular slots, 154, formed by the top plate, 111, and the notches, 153, in the side support structures, 151. These rectangular slots, 154, are dimensioned, now referring to FIG. 4, to accept the protruding flange section, 504, of the perpendicular joist support modular element, 501, when it is engaged, referring now to FIG. 1 b, with a plywood support modular element, 101. Referring now to FIG. 4, the perpendicular joist support modular element, 501, further comprises one or a plurality of nailing holes, 505. These nailing holes may be dimensioned such that they will accept fastening means, such as nails, at an angle with respect to the planes formed by the vertical sides, 509, of the steel rod, 502, as it is formed into the rectangular enclosure, 503. When a nailing hole is formed at such an angle, a nail may be driven through it, through a section of joist material contained within the rectangular enclosure, 503, and into a joist on which the supporting plywood support modular element is mounted. In this way, such a nail may both provide vertical support for the perpendicular joist support modular element, 501, and may prevent the lateral motion of a perpendicular joist support modular element, 501, with respect to the joist on which the supporting plywood support modular element is mounted. As illustrated in FIG. 4, two nailing holes, 505, may be dimensioned such that they will accept and guide fastening means, such as nails, at angles in opposite directions with respect to the planes formed by the vertical sides, 509, of the steel rod, 502, as it is formed into the rectangular enclosure, 503. In this way, if the perpendicular joist support modular element, 501, were to be rotated 180 degrees around its central vertical axis, a nailing hole will still be available to guide a fastening means, such as a nail, through it, through a section of joist material contained within the rectangular enclosure, 503, and into a joist on which a supporting plywood support modular element is mounted.

FIG. 4 a illustrates a perpendicular joist support modular element, 501, engaged with, resting on, and depending for vertical support on, a side support structure, 151, of a plywood support modular element, 101.

FIG. 4 b illustrates an alternative means of rendering fastening holes in an embodiment of the perpendicular joist support modular element, 501, such that fastening means, comprising nails of various sizes, may be nailed at an angle through the fastening hole, through a section of joist material contained within the rectangular enclosure, 503, and into a joist on which a supporting plywood support modular element is mounted. The widened slit, 506, can be formed by means such as punch press. A cross member, 507, can be inserted into the widened slit, 506, at its widest point, and then welded into place, ensuring that the slit will not be narrowed due to impact and load forces.

FIG. 4 c illustrates a perpendicular joist support modular element, 501, having an upper protruding flange, 504, engaged with, resting on, and supported vertically by a plywood support modular element, 101, which in turn is mounted on and supported by a joist section, 201, of a primary support joist, 301, and is further secured to and prevented from horizontal movement with respect to the joist section, 201, by means of the finishing nail, 103. A shorter perpendicular joist section, 403, is perpendicular to the joist section, 201, and has one end enclosed and supported vertically by the rectangular enclosure, 503, of the perpendicular joist support modular element, 501.

FIG. 4 d is similar to FIG. 4 c, but only visible surfaces and edges are rendered. FIG. 4 d further illustrates a perpendicular joist support modular element, 501, enclosing and providing vertical support for one end of a longer perpendicular joist section, 401, perpendicular to a supporting joist section, 201, that is supporting a plywood support modular element, 101. An angled finishing nail, 508, is driven through an angled nailing hole, 505, into and through the longer perpendicular joist section, 401, and into the supporting joist section, 201. As a result, the perpendicular joist support modular element, 501, and the longer perpendicular joist section, 401, are supported vertically by both the angled finishing nail, 508, and, referring now to FIG. 4 c, by the upper protruding flange, 504, of the perpendicular joist support modular element, 501.

FIG. 4 d further illustrates a shim pad, 402, of the present invention, similar to the shim pad, 171, described earlier with reference to FIG. 2. Referring now to FIG. 4 d, the shim pad, 402, is dimensioned to be placed on the top side of a perpendicular joist section, 404, and to support formwork plywood sheets at the same level as the top of the top plate, 111. Because the top side of perpendicular joist sections, 404, are slightly lower than the upper sides of the primary support joists, by both the thickness of the top plate, 111, and, referring now to FIG. 4, the depth of the notch, 153, in the side support structure, 151, referring now to FIG. 4 d, the shim pads, 402, used with perpendicular joist sections, 404, of the present invention must be dimensioned accordingly, and will be thicker than the shim pads, 171, used on primary supporting joists. Shim pads may be produced in a range of thicknesses, to accommodate standard and/or known dimensions, such as the thickness of the top plate, 111, and, referring now to FIG. 4, the depth of the notch, 153, and/or known or predicted joist and other formwork deflections based on engineering data and conventions. Alternatively, the selection of shims of appropriate thickness for perpendicular joist sections, 404, may be determined or influenced by taking on-site measurements.

FIG. 4 a-1 illustrates a second embodiment of a plywood support modular element, 101, and a second embodiment of a perpendicular joist support modular element, 501, of the present invention. The plywood support modular element, 101, further comprises two full width side support structures, 156, each having deeper notches, 157, and full length flange sections, 158. The perpendicular joist support modular element, 501, further comprises a short downward flange section, 511, dimensioned such that it can be slid through the rectangular slots, 154, formed by the deeper notches, 157, in the full width side support structures, 156, when the full width side support structures, 156, are attached to the top plate, 111. The perpendicular joist support modular element, 501, further comprises a gap, 513, between the downward flange section, 511, and the joist side vertical face, 514, of the perpendicular joist support modular element, 501, dimensioned to the thickness of the full width side support structure, 156, such that when the short downward flange section, 511, is inserted through the rectangular slot, 154, the perpendicular joist support modular element can then be slid down such that it is supported vertically by the full width side support structure, 156, and is held in a rigid vertical position by a tight interlocking of the joist side vertical face, 514, and the short downward flange section, 511, with the full width side support structure, 156. It should be noted that for this embodiment of the plywood support modular element, 101, because the deeper notches, 157, are on opposite sides of the top plate, 111, a single angled nailing hole, 505, can always direct a nail through the joist section being supported by the perpendicular joist support modular element, 501, and into the joist section on which the plywood support modular element, 101, is depending.

FIG. 4 a-2 illustrates a full width side support structure, 156, of a said second embodiment of a plywood support modular element, 101, engaged with a said second embodiment of a perpendicular joist support modular element, 501. Because the perpendicular joist support modular element, 501, rests at the bottom of the deeper notch, 157, in the full width side support structure, 156, the short downward flange section, 511, constrains the perpendicular joist support modular element, 501, from moving horizontally with respect to the plywood support modular element, 101.

FIG. 4 d-1 illustrates the said second embodiment of a plywood support modular element, 101, and the said second embodiment of a perpendicular joist support modular element, 501, engaged with a joist section, 201, and a perpendicular joist section, 404. Due to the deeper notch, 157, in the full width side support structure, 156, the upper side, 406, of the perpendicular joist section, 404, is recessed below the bottom of the top plate, 111, of the plywood support modular element, 101, requiring a thicker shim pad, 405, to support top sheathing plywood on the plane of the top plate, 111, and the shim pad, 171. It should be noted that while a finishing nail, 103, and an angled finishing nail, 508, are illustrated in FIG. 4 d-1, in some circumstances the invention may be practiced without the use of such nails. In particular, because, as described with reference to FIG. 4 a-2, the said second embodiment of the perpendicular joist support modular element, 501, is constrained from horizontal movement with respect to the said second embodiment of the plywood support modular element, 101, and, referring now to FIG. 4 d-1, is constrained from moving vertically during use by poured concrete resting on upper plywood sheathing that is supported by the thicker shim pad, 405, the use of the nailing hole, 505, in the said second embodiment of the perpendicular joist support modular element, 501, is often unnecessary.

FIG. 5 is a top view of a formwork structure comprising a grid of rectangles, 453, formed by primary support joists, 301, spaced at four feet apart, and supporting perpendicular joist sections, 404, also spaced at four feet apart. Plywood support modular elements, 101, are mounted on both the short plywood edge primary support joists, 303, and the perpendicular joist sections, 404, and are spaced approximately two feet apart. As identified by an enlarged circle at the upper left of FIG. 5, illustrated separately as FIG. 5-1, at intersections of a short plywood edge primary support joist, 303, with two ends of perpendicular joist sections, 404, referring now to FIG. 5, all of the perpendicular joist sections, 404, have a perpendicular joist support modular element, 501, of the present invention, enclosing and engaged with the perpendicular joist sections, 404, at both ends of each perpendicular joist section, 404, and in turn, these perpendicular joist support modular elements, 501, are engaged with, resting on, and supported vertically by the adjoining plywood support modular elements, 101, as described above with reference to FIG. 4 d. The adjoining plywood support modular elements, 101, are in turn mounted on the short plywood edge primary support joists, 303. As identified by an upper enlarged circle at the upper right of FIG. 5, illustrated separately as FIG. 5-2, shim pads, 171, are placed on the upper sides of the short plywood edge primary support joists, 303, referring now to FIG. 5, at each midpoint between two plywood support modular elements, 101, mounted on a short plywood edge primary support joist, 303. As identified by a lower enlarged circle at the upper right of FIG. 5, illustrated separately as FIG. 5-3, shim pads, 402, are placed on the upper sides of the perpendicular joist sections, 404, referring now to FIG. 5, at each midpoint between the center and the edges of a perpendicular joist section, 404. The set of shim pads, 171, and the set of shim pads, 402, are all dimensioned such that before any camber is added to the structure by means of shoring, their upper surfaces are all in the same horizontal plane.

It should be noted that while the primary support joists, 301, of FIG. 5, are shown as continuous, these elements may alternatively be sectioned such that two sections abut at a shoring point. This sectioning of the primary support joists, 301, facilitates setting a slight camber, to be determined by engineering calculations, in the span of the short plywood edge primary support joists, 303, such that when the shoring and formwork are removed, the camber will compensate for the deflection that occurs in the slab due to the weight of the concrete, with the result that the finished suspended slab will be horizontal and flat, rather than dish shaped.

FIG. 4 e and FIG. 4 f illustrate the sectioning of the primary support joists, 301, of FIG. 5. FIG. 4 e is an exploded view of a structure comprising an intersection of two primary support joist sections, 305, with two perpendicular joist sections, 404, a plywood support modular element, 101, two perpendicular joist support modular elements, 501, a primary support joist section shoring tray, 452, and a vertically supporting shoring member, 451. FIG. 4 f illustrates the structure resulting from the assembly of the elements of FIG. 4 e. The primary support joist sections, 305, depend for vertical shoring to grid engagement means on the primary support joist shoring tray, 452, and, in turn, on the vertical shoring member, 451. The perpendicular joist sections, 404, depend on the perpendicular joist support modular elements, 501, which, in turn, depend on the plywood support modular element, 101, which, in turn, depends on the primary support joist sections, 305. Because the primary support joist sections, 305, are discontinuous, the camber of the structure can be set as needed by means of adjusting the height of the vertical shoring member, 451.

FIG. 5 a illustrates the formwork structure of FIG. 5, shown as dashed lines, beneath the formwork plywood sheets, 351, shown as solid lines. As seen in FIG. 5, a rectangular array of four foot square plywood sheathing areas is rendered, such that each plywood rectangle is supported on all sides and edges except the sides nearest to and parallel to the girders, 302, by plywood support modular elements, 101, spaced two feet apart. It should be noted that, if needed, additional perpendicular joist sections, 404, having plywood support modular elements mount on their midpoints, can be added to the formwork structure illustrated in FIG. 5, such that they are parallel and adjacent to the girders, 302, and such that plywood rectangles adjacent to girders are also supported on all sides and edges by plywood support modular elements spaced two feet apart. Generally a plywood rectangle supported continuously on three sides, or four sides, will deflect less than the same rectangle supported continuously on only two sides. For many applications involving slab thicknesses of a foot or less, the formwork structure of FIG. 5 will adequately minimize deflection. As an additional alternative, it is possible to shore each plywood rectangle at the center points, as illustrated by the direct plywood shoring points, 601, illustrated in FIG. 5.

FIG. 4 g is a perspective illustration of a four foot by four foot grid square, 453, referring now to FIG. 5, illustrating a larger grid structure comprising a plurality of grid squares, 453. Referring now to FIG. 4 g, the interior sides, 106, of the plywood support modular elements, 101, positioned at the midpoints of the joist sides forming the grid square, 453, provide deflection support, referring now to FIG. 5 a, for the plywood sheets, 351, that are placed above the grid squares, 453, in the process of preparing the formwork for a pour. FIG. 4 g further illustrates that the use of plywood support modular elements, 101, serves to prevent lateral motion of each joist member that is supporting a plywood support modular element, adding stability to a shored formwork structure of the present invention. Additional stability can be added to the formwork structure, as needed, by use of the lower nailing holes, 505. Referring now to FIG. 4 f, optimal stability can be achieved by using as fastening means both the upper nailing hole, 112, in the plywood support modular element, 101, and the lower nailing hole, 505, in the perpendicular joist support modular element, 501, referring now to FIG. 4 g at each intersection of joists, referring now to FIG. 4 f, together with a means such as the primary support joist shoring tray, 452, that is secured to a vertical shoring member, 451, by fastening means such as nailing. Referring to FIG. 4 g, it should be noted that the illustrated plywood support modular elements having interior sides, 106, can be mounted at the midpoint between the points of intersection of a joist or joist section, or at other points between the points of intersection of a joist or joist section.

FIG. 4 g-1 further illustrates that vertically dimensioned plywood support modular element supporting shim pads, 172, can be placed beneath lower plywood support modular elements, 115, to raise their top plate upper sides, 117, to the level of the plane formed by the top plate upper sides, 117, of higher plywood support modular elements, 116. Ensuring that some or all plywood support modular element top plate upper sides, 117, in a grid structure are on the same horizontal plane serves to optimize the prevention of lateral motion of all joist members. It should be understood that the required height of plywood support modular element supporting shims, 172, may vary. In particular, referring now to FIG. 4 d-1, for embodiments of plywood support modular elements, 101, having side support structures with deeper notches, 157, thicker shim pads, 405, may be required. It should be understood that side support structures having deeper notches, 157, may be taller, to ensure, referring now to FIG. 1 c, that the plywood support joist enclosing cavity, 102, is deep enough to enclose, referring now to FIG. 4 d-1 both the thicker shim pad, 405, and a sufficient depth of the joist section, 404. It should be noted that the plywood support modular element supporting shims, 172, may be placed beneath the plywood support modular elements, and after the formed slab is partially cured, the supporting shims, 172, may be slid out from under the plywood support modular elements, 101, providing means for disengagement and immediate reuse of the perpendicular joist support modular elements, 501, and the formwork elements supported by them.

FIG. 5 b is similar to FIG. 5, but illustrates that the spacing of the primary support joists, 301, can be reduced, if needed, to further minimize deflection, or in response to engineering attributes of a particular project. Perpendicular joist sections can be sized accordingly.

Under the heading: background of the invention, regarding design parameters: required and/or desirable attributes of a formwork system for CIP horizontal concrete slabs were characterized. These required or desirable attributes will now be quoted and commented on with respect to the present invention.

Regarding: “a modular design, such that components can be used to achieve some, but not all, of the benefits of the full system.” The present invention features a plywood support modular element that functions to center plywood sheathing on the center lines of supporting members. This is an important contribution to the value of formwork systems; value is added whenever the risk of blown formwork can be reduced or eliminated.

Regarding: “ . . . minimal or no need for nails to secure plywood to joists; . . . ” the use of plywood support modular elements alone can reduce the nailing requirement. Combined use of the plywood support element and the perpendicular joist support modular element provide for the ability, if necessary, to support a rectangular grid of formwork plywood sheets on all sides, significantly reducing deflection. This can also reduce nailing requirements, particularly with respect to embodiments of the plywood support modular element and the interlocking perpendicular joist support modular element as described above with reference to FIG. 4 a-1, FIG. 4 a-2, and FIG. 4 d-1.

Regarding: “ . . . assurance that when plywood sheets abut, their lines of abutment are parallel to and centered on supporting joists; . . . ” The present invention accomplishes this.

Regarding: “ . . . practicality of using for formwork elements lighter and less expensive 2× lumber rather than heavier and more expensive 4× lumber; . . . ” as described and illustrated in the specification, the present invention makes the use of 2× lumber practical. In particular, embodiments of the plywood support modular element ensure that top plywood sheathing will not fall over the edge of a joist, and not deflect beyond acceptable parameters.

Regarding: “ . . . assurance that any deflection resulting during the pouring of concrete will not pull a plywood sheet over the edge of a supporting joist; . . . ” The present invention provides this assurance.

Regarding: “ . . . means to minimize plywood deflection to within acceptable parameters; . . . ” the present invention provides means for a significant decrease in deflection.

Regarding: “ . . . means to set the level of the formwork upper surface to provide for any required camber, as determined by architectural and engineering specifications, such that when the formwork is removed, and normal deflection occurs in the horizontal slab, the resulting surface of the slab will be flat.” The present invention provides for this.

Regarding: “ . . . means to ensure optimal stability of a shored formwork structure . . . , the present invention comprises a grid structure, as illustrated in FIG. 4 g, such that the weight of concrete from above, the use of the nailing holes, 112 and 505, at each joist intersection, and the use of means of attaching vertical shoring members to the grid structure as illustrated in FIG. 4 f, can be used in combination to achieve optimal stability. It should be understood that engineering requirements for particular construction applications may be such the full stabilizing effect of all of the above mentioned means may not be needed.

Regarding: “ . . . means to allow for early removal of cross member joist sections, while leaving in place primary supporting joists, when the concrete has set and cured to a point that the cross member joist sections are no longer needed to prevent deflection between primary supporting joists.” Although concrete cures fully over multiple weeks, for spans of up to four feet, reinforced concrete will typically cure within a few days to the strength required to support a four foot section without respect to deflection, allowing perpendicular joist sections supported by perpendicular joist support modular elements to be removed and redeployed. Thus, the present invention provides this advantage.

While embodiments of the present invention have been described, it should be appreciated that various modifications may be made by those skilled in the art without departing from the spirit and scope of the present invention. Accordingly, reference should be made to the claims to determine the scope of the present invention. 

1. A formwork system for forming Cast In Place horizontal concrete slabs, comprising: a. one, or a plurality, of plywood support modular elements, each said plywood support modular element mounted on top of, and depending for vertical support on, a first joist section, and, b. one, or a plurality, of perpendicular joist support modular elements, each said perpendicular joist support modular element engaged with, and depending on vertical support from, a plywood support modular element, and, c. each said perpendicular joist support modular element enclosing, and providing vertical support for, one end of a second joist section perpendicular to the said first joist section supporting the said engaged plywood support modular element.
 2. The formwork system of claim 1, further comprising plywood support modular elements having central protruding nails that abut top plywood sheathing.
 3. The formwork system of claim 1, further comprising a grid of rectangles formed by joists and/or joist sections.
 4. The formwork system of claim 3, further comprising one, or a plurality, of shoring members, vertically supporting the intersection of one, or a plurality, of intersections of the said joists and/or joist sections.
 5. The formwork system of claim 4, further comprising means of setting the camber of one, or a plurality, of the said intersections of joists and/or joist sections.
 6. The formwork system of claim 3, further comprising one, or a plurality, of plywood support modular element mounted at a point between the points of intersection of one, or a plurality, of the said joist and/or joist sections.
 7. The formwork system of claim 6, further comprising fastening means for attaching each plywood support modular element to its supporting joist and/or joist section.
 8. The formwork system of claim 3, further comprising one, or a plurality, of plywood support modular elements mounted at the midpoint between the points of intersection of one, or a plurality, of the said joist and/or joist sections.
 9. The formwork system of claim 7, further comprising a fastening means for attaching the bottom of each perpendicular joist support modular element to the joist and/or joist section supporting the said engaged plywood support modular element.
 10. The formwork system of claim 3, further comprising one, or a plurality, of vertically dimensioned support shims beneath one or a plurality of the said plywood support modular elements, such that the upper surfaces of a plurality of plywood support modular elements are in the same horizontal plane.
 11. The formwork structure of claim 3, the said plywood support modular element(s) further comprising a top plate, the said plywood support modular element further comprising two side support structures, each of the said side support structures having an upper notch, each of the said side support structures forming together with the said top plate, a plywood supporting flange structure perpendicular to the said first joist section, extending outward from the upper side of the said first joist section, and supported horizontally by the vertical side of the said first joist section, each of the said flange structures having a central slot beneath the top plate, the said central slot having a perimeter delineated by the bottom surface of the said top plate, and the peripheral edges of the said notch.
 12. The formwork structure of claim 11, the said perpendicular joist support modular element(s) further comprising a downward flange section, the said perpendicular joist support modular element(s) further comprising a gap between the said downward flange section and the joist side vertical face of the said perpendicular joist support modular element(s), the said gap being dimensioned to the thickness of the said side support structure.
 13. The formwork structure of claim 3, further comprising one, or a plurality, of vertically dimensioned plywood support modular element supporting shim pads.
 14. The formwork structure of claim 3, further comprising one, or a plurality, of vertical shoring to grid engagement means.
 15. The formwork structure of claim 3, further comprising means for disengagement and immediate reuse of one or a plurality of the said perpendicular joist support modular elements, and formwork elements supported by them.
 16. A formwork structure for forming Cast In Place horizontal concrete slabs, comprising a plywood support modular element, mounted on, and depending for vertical support on, a first joist section, the said plywood support modular element further comprising: a. a top plate, and b. two side support structures, each having an upper notch, and c. a central joist enclosing cavity, and d. the said notch of each of the said side support structures, forming together with the said top plate, a slot, and, e. each of the said side support structures forming together with the said top plate, a flange structure perpendicular to the said first joist section, extending outward from the upper side of the said first joist section, and supported horizontally by the vertical side of the said first joist section.
 17. The formwork structure of claim 16, further comprising a nailing hole through the top plate, and adjoining the said first joist section.
 18. The formwork structure of claim 16, further comprising an outer peripheral nailing hole through one or both of the said side support structures. 